Mass clamp for gravity meters



`2 sheets-sheetv 1 7 Dcn s, 1942.,

H A. lvmslalz` MASS CLAMP FOR GRAVITY METERS Filed March 6, 1940 Dec. 8, 1942. H. A. MAI-:DER

MASS CLAMP FOR GRAVITY METERS y Filed M-mh s, 1940 2 sheets-sheet 2 www lenig/Maeda Patented Dec. 8, 1942 2.3104337 Mass CLAMP Fon GRAVITY METERS Henry A. Maeder, Dallas, Tex., assignor, by mesne assignments, to Socony-Vacuum il Company, Incorporated `poration of New York .Appucstipn March s, 1940, serial Nt, 322,497

This invention relates to hydraulic clamps and more particularly to hydraulic clamps for gravity meter masses.

In making a geophysical survey using a gravity meter which includes a mass bar suspended at the end of a torsion menier or members, it is customary to set up the meter at a rst or originalbase station, adjust the torsion members to the critical point and calibrate the instrument. The meter is then moved to various other stations and a reading taken at each station without, of course, further adjustment of the torsion members. These readings vary but slightly and l are taken in tenths of millidynes. It has been found that unless the mass is held absolutely rigid during transportation of the meter, the physical characteristics of the torsion member or members are altered suillciently to render the readings useless. It is therefore necessary to provide a clamp for the mass bar that will rigid-I ly hold the` mass so thatA the torsion elements will be protected. y

By the present invention the lmass bar of a gravity meter is clamped in such a manner that it will be positively held against vibration when moving the instrument from 'one place to another, Brieiiy the clamp includes a pair of clamping members located on opposite sides of the bar and adapted to be forced against the bar by hydraulic pressure, one of the members being limited in its travel by stops which allow it to move just far enough toI center the bar. The member having` the stops is opposed by a weaker spring than the othermember and consequently, upon application of hydraulic pressure, the first member will be moved agalnstits stop before the other member is moved. Because of the superior moving force exerted on the aforementioned first member, it will be heid against its stop throughout the period ofclamping.. Means are'also provided to prevent sticking of the mass bar to the clamping surfaces and thus violentl disturbance of the bar upon its release is avoided.

Itis an object of the present invention to pro.-

yvide means for rigidly clamping an article suchA as a gravity meter mass.

Another object is the provision of a gravity meter having hydraulically operated means for clamping the' mass in such a manner that it will be positively held against vibration relative to the housing.

It is a further object of theinvention to provide a clamp which includes means designed to prevent the clamped article from adhering to the z clamping surface upon release thereof.

An additional object is' to provide a clamp which includes a pair of opposed hydraulically operated pistons with means to control their operation whereby an article will always be N ew York, N. Y., a cor- 3 Claims. (Cl. m35-L4) clamped in the same position relative to the cylinders containing said pistons. J

Another object is the provision of a hydraulic clamp having a pair of opposed pistons in which means are included to adjust the position of the pistons relative to the fix-ed base of the clamp.

Further objects and advantages will become apparent in the following description of the invention with reference to the accompanying drawings in which:

y Figure 1 is an isometric view of the invention as applied to a gravity meter of the biiilar type.

Figure 2 is an elevation of the clamp partially broken away to show the details oi?A the piston assemblies; and

Figure 3 is a section view nate piston assembly.`

In Figure 1 a gravity meter is shown as including a support 4 which is mountedv on theA meter housing (not shown). The bar mass 5 is showing an altersuspended from the support 4, by-torsion mem bers 6 which are secured to adjusting elements I carried by the support. 'I'he elements 'I have been adjusted in a manner well known to the -art to position bar 5 as shown so that it will move a short distance vertically in response to variations in the force of gravity.l Other details of the met-er such as the reading mechanism are well known and are here omitted since they are unnecessary for a complete disclosure vention.

- One end of bar 5 extends between the adjacent of the inends of a pair of axially aligned, horizontal cylinders 8 and 9. 'I'hese cylinders are mounted on or formed as' part of a movable base I0, (Figures land 2) with the adjacent ends of the cylinders being spaced to permit the bar 5 to hang freely when unclamped. Movable base I0 is slidably mounted on a iixed base Il which is securedjto the meter housing' (not shown) and the two bases are connected by adjusting screw I2 .which is' operated by lhandle I3. Rotation ofthe adjusting screw will thus shift the cylinders axially vand thereby free hanging of bar 5 when it is in its operating position may be assured. A

Referring now to Figure 2. a piston I4 is positioned within cylinder-8 and is normally held in the position shown by spring I5. vA pin I 6 is slidably'. mounted in a bushing I'I carried in the right end of piston I4. This pin is normally held in the position shown, with its rounded or pointed end'extending slightly past the fiat faceof the piston, by spring I8. Piston I4 has an axial bore I9 and the cylinder cap 20 has a tubular portion 2 Iv slidably fitted into said bore. The tubular portion 2| is connected to an oil line 22 and thusl.

, when oil passes therethrough into the cylinder under pressure. Piston Il will be moved tothe right against the force of spring I5. A^`shoulder 23 on the left end of piston Il engage shoulder 24 on the cylinder wall to limitv movement of the piston to the right.

Another piston 25 is located within cylinder l and held in the position shownby spring 28. The left end of piston 25 is equipped with a bushing 21, pin 28, and spring 29 similar to thosein i the right end of piston I4. Piston 25 also has ,an axial bore 30 intov which is slidably fitted a tubular portion 3l of cylinder cap32'. Oil line 83 is connected to tubular portion 3i and thus when oil passesv therethrough into the cylinder under pressure, piston 25 will be moved to the left.

Drains 48 are provided in both cylinders to remove any oil which may have leaked out of the pistons. Oil lines 22 and 83 are both connected to chamber 84-whlch is equipped with a pressure gauge 35 and an inlet 3B for receiving oil from a pressure source. r

When it is desired to clamp the bar 5 in place,. oil is fed through, chamber 84 and lines 22 and 33 to cylinders 8 and 9. Now the piston springs are so constructed that spring I5 is weaker than spring 28. 'I'hen as the oil pressure is applied,

piston I4 will be operated first and moved to the right until shoulder 23 engages shoulder 24. Thereafter, piston 25 will be moved to-the left asomar 2. wams cylinders :una n m pistons u' and 4l, respectively. Each of these pistons has a pin 4I, bushing 42 and spring 4l in its clamping end.

its cap and tends to move piston 39 t'o theleft.v Another spring 41 tends to move piston 4Il to inder.

and the bar 5 will be engaged on oppositesids by pins IB'and 28.' Springs I8 and 28 will then be compressed allowing the fiat end i'ares of the two pistons to firmly clamp the iiat sided har 5 between them. It is to be noted that movement of piston 25 to. the left is limited only by the' vcompression length of spring 28 andtherefore servingthe same purpose as described for pins Il and 28, bushings I1 and 21, and springs I8 and 29 in Figure 2. A bellows 44 lconnects each piston with ,its cylinder cap 4s to form' s nexible, oil tight chamber, the caps, of course, being ladapted for connection to a common oil supply to feed oil underpressure to the interior of the bellows. A Spring extends from piston I5 to the right. However, the natural Aspring of the bellows hold their respective pistons in the posirtions shown. In this construction, spring 48 is ence to Figure 2. f

Although the present invention has been illustrated and described as applied to a gravity meter of the bifilar type, itis obvious that it can be used with a meter having a singleV torsion memberand that other applications thereof can be made. It is the intention, therefore, to limit the scope of the invention only as set forth in the attached claims.

sufficient movement is available to clamp the bar. It will also be seen that since spring I5 -is weaker than spring 26, Aequal cil pressure in the two pistons will result in a greater resultant iorce on piston I4 to hold it with shoulder 22' against shoulder 24. Consequently bar 5rwill be clamped each time in the same position relative to the cylinders. l

When it is desired to release bar 5, the oil pressure is removed whereupon springs I5 and 26 force their respective pistons back to normal positions. In order to hold bar 5 rigidly, it is imperative that the flat end faces of the pistons ,A engaging the flat sides of the bar be of an apy preciable area. However, when the barlis to be released it will tend to adhere or stick-to the clamping faces. If plain -end faces were used on the pistons, the sticking of thebar would re. suit in a jerking or sudden horizontal swinging thereof when actually released. Considerable time` would then be consumed in waiting" for the bar to .become'stationary before taking a reading. 'I'he present invention overcomes this difficulty by. the provision of vpins I6 and 28. Examination of the drawings will disclose that when the end faces of the piston break away from the bar, pins I8 and 28 still remain in engagement with the bar .holding it steady. As the pistons Vmove `further toward their normal positions, the pins will be removedfrom `the bar but their smaller I claim:

l. Ina clamp, apair bers, each having a surface for engaging the article to be clamped, means for moving each of said members toward the other includingra system for exerting equal hydraulic pressure onsaid members, individual spring means lassociated with each member in-oppositionA to said hydraulic pressure, said individual spring means being of unequal strength, whereby one of said members will move prior to the other, means for limiting the totalmovement of said prior moving member,

and means yieldably vprojecting from said engaging .surfaces of the clampingmembers for' engaging the article to be clamped.

2r. In a clamp, a pair of spaced clamping members, each having a surface for engaging the article to be clamped, means for movingl each oi Isaid members toward the other including a system for exerting equal hydraulic pressure. on said members, individual spring means associated the article to be clamped, and resilient means for resisting the movement of the yieldably project- 1 'ing means in a direction away from the article to sticking. of the'bar thereto. In addition, the

position of the cylinders relative to the end of the v bar may be adjusted by screw I2' so that the bar will be clamped in approximately the same position it heldwhen free. As` a consequence,

V swinging or the bar upon its release will be reduced to a minimum.

A different construction is illustrated in Figure Bwhich discloses a pair of cylinders 31 and 38 which mayreplace cylinders 8 and 8 in Figure be clamped.

3. In a clamp, a pair of spaced clamping members,means for moving each of said members toward the other including a system for exerting equal hydraulic pressure on said members, individual spring means associated with each mem- J ber in opposition to said hydraulic pressure, said individual spring means being of unequal strength, whereby one of said members fwill move prior to the other, and means forlimiting the.V

total movement oi' said prior moving member. HENRY A. MAEDER.

'of spaced clamping mem- 

